Use thread-local allocations for all multi-threaded builds

Use thread-local allocations for all multi-threaded builds

This change affects only builds by configure and CMake.

* CMakeLists.txt [CMAKE_USE_PTHREADS_INIT]: Handle *-*-*linux* and
*-*-nacl* targets in the same way as x86-*-linux*.
* CMakeLists.txt [CMAKE_USE_PTHREADS_INIT] (THREAD_LOCAL_ALLOC): Define
macro (and add thread_local_alloc.c to SRC) for *-*-aix*, *-*-hpux11*,
*-*-openbsd*, *-*-freebsd*, *-*-netbsd*, *-*-irix* targets.
* configure.ac [THREADS=posix] (THREAD_LOCAL_ALLOC): AC_DEFINE for
*-*-*linux*, *-*-nacl*, *-*-aix*, *-*-openbsd*, *-*-netbsd*, *-*-irix*
targets.
* configure.ac [THREADS=posix && *-*-freebsd*]: Remove AC_MSG_WARN that
threads are not fully supported by GC.
* CMakeLists.txt [CMAKE_USE_PTHREADS_INIT && *-*-freebsd*]: Likewise.
* configure.ac [THREADS=posix && *-*-osf*] (THREAD_LOCAL_ALLOC):
Define even if enable_parallel_mark is false.
* CMakeLists.txt [CMAKE_USE_PTHREADS_INIT && *-*-osf*]
(THREAD_LOCAL_ALLOC): Likewise.
* configure.ac [THREADS=aix] (THREAD_LOCAL_ALLOC): AC_DEFINE.